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63 Cards in this Set

  • Front
  • Back
Pharmacology
The science dealing with interactions between living systems and molecules, especially chemicals introduced from outside the system
Medical Pharmacology
Science of materials: used to prevent, diagnose, and treat disease; that cause disease; used as molecular probes for the study of normal biochemistry and physiology
Toxicology
Branch of pharmacology that deals with the undesirable effects of chemicals in biologic systems
Drug
Any small molecule that, when introduced into the body, alters the body's function by interactions at the molecular level
Pharmacodynamics
Responsiveness of receptors to drugs and the mechanism by which these effects occur. "What a drug does to the body"
Pharmacokinetics
Absorption, distribution, metabolism and excretion of inhaled or injected drugs. "What the body does to a drug"
Stereochemistry
Study of how molecules are structured in three dimensions
Chirality
Unique subset of stereochemistry designating molecules that have a center (or centers) of three dimensional asymmetry. Chirality is the structural basis for enantiomerism
Enantiomers
A pair of molecules existing in 2 forms that are mirror images of one another but cannot be superimposed (are of opposite shapes)
Stereoselectivity
The direction in which they rotate polarized light; clockwise rotation=dextrorotary, d+ or levorotary l- (Ex. Right and Left hand)
Stereospecificity
The absolute configuration is specified by the designation of sinister (S) or rectus (R)
Racemic Mixture
When 2 enantiomers are present in equal proportions (50:50 mixture) Ex. Epi, Ketamine
Absorption
Movement into the body from the site of administration
Distribution
Movement between different parts of the body
Biotransformation
Alters activity of drug and may prepare it for excretion
Excretion
Movement out of the body
Name the 4 major mechanisms by which drugs move across barriers
Aqueous diffusion (passive)
Lipid diffusion (passive)
Active Transport
Facilitated diffusion
Aqueous Diffusion (Passive)
Only drugs of very small molecular weight (100-150) can diffuse across epithelial membranes (cornea, GI tract, bladder). Epithelial cells are connected by tight junctions that do not permit larger molecules to enter. Most capillaries have very large aqueous pores allowing molecules as large as 20-30,000 to enter
Lipid Diffusion (Passive)
Movement across cell membranes by solution in the lipids of the membrane, with passive transfer across the lipid driven by a concentration gradient. Drugs with higher lipid solubilities (relative to water solubility) favor this mode of transfer. Move down concentration grandient High--Low
Fick's Law of Diffusion (magnitude of flux)

*Know proportional relationships
J magnitude of flux = P Permeability coefficient x A Area across which diffusion occurs x (C1-C2) Concentration gradient divided by membrane thickness x square root of molecular weight
Lipid solubility (permeability coefficient) is greatly influenced by what?
Degree of ionization
Which type of molecule crosses the lipid membrane more readily: Unionized (uncharged) or Ionized (charged)
Unionized (uncharged)
Many drugs are either weak bases or weak acids. Describe their relationship pH
The pH of the environment greatly influences the degree of ionization and thus solubility
At an alkaline pH, acidic drugs tend to be...
Highly ionized (charged)
Ex. sodium thiopental
At an acidic pH, alkaline drugs tend to be...
Highly ionized (charged)
Ex. local anesthetics
Henderson-Hasselbach
Equation describing the degree of ionization in a particular pH environment
pKa
the pH at which a molecule is 50% ionized and 50% unionized
Acids
Proton donors
pH = pKa + log A- (acid) divided by HA (protonated acid)
Ex. Barbiturates, ASA
Bases
Proton donors
pH = pKa + log B (base) divided by BH+ (protonated base)
Ex. Local anesthetics, opioids
pH = A- divided by HA
A- (unprotonated, charged, ionized) divided by
HA (protonated, uncharged, unionized)
pH = B divided by BH+
B (unprotonated, uncharged, unionized) divided by
BH+ (protonated, charged, ionized)
pKa 1 for Acid
pKa 1 = .5/.5
Acid (unprotonated, charged, ionized) over (protonated, uncharged, unionized)
pKa -1 for Acid
pKa -1 = .1/.9
pKa +1 for Acid
pKa +1 = .9/.1
pKa 1 for Base
pKa 1 = .5/.5
Base (unprotonated, uncharged, unionized) over (protonated, charged, ionized)
pKa -1 for Base
pKa -1 = .1/.9
pKa +1 for Base
pKa +1 = .9/.1
Ion trapping
Concentration difference of total drug can develop on 2 sides of a membrane that separates fluids with different pHs. A drug enters a lipid membrane through a pH environment that renders the drug uncharged---after crossing the membrane into a more acidic environment, the drug becomes charged and thus unable to go back across the membrane.
Give 2 examples of ion trapping in the body
1. Oral administration of weak bases (opioids) becomes highly ionized (charged) in the stomach and thus "trapped" in the intestine
2. Some drugs cross the maternal placenta into the fetal circulation which has a lower pH. The drugs become highly ionized (charged) and thus "trapped" within the fetal circulation
Active transport
Transports molecules across membranes in an energy-dependent process. The process is molecule specific, saturable, and can occur against a concentration gradient. There is a limit to the effectiveness of dose
Facilitated diffusion
Similar to active transport in that it is carrier-mediated, specific, and saturable but it does not require energy and cannot transport against a concentration gradient. Pinocytosis (receptor-mediated endocytosis) is an example of facilitated diffusion. Also insulin release b/c it doesn't require energy, but needs a 2nd messenger
VRG
CO
BM
Onset
Vessel Rich Group-1
CO-75%
BM-10%
Brain, heart, liver, kidney, endocrine glands
Onset-rapid
MG
CO
BM
Onset
Muscle Group-2
CO-19%
BM-50%
Muscle, skin
Onset-rapid
FG
CO
BM
Onset
Fat Group-3
CO-6%
BM-20%
Fat
Onset-Slower
VPG
CO
BO
Onset
Vessel Poor Group-3
CO-less than 1%
BM-20%
Bone, ligament, cartilage
Onset-Slowest
Which compartment are drugs eliminated from?
Central compartment
k
Represents the different rate constants for intercompartmental transfer of drug as well as the elimination rate constant. Movement of drug
What are the pharmacokinetic compartment models useful for?
Explaining the changes in plasma concentration that occur after a drug is administered. Compartments are hypothetical and cannot actually be measured
Hypnosis
Hypnotic drug
Sleep
Puts pt to sleep
Drug in Body
1/2 Life
Drug in Plasma
1/2 Time
Rapid Distribution Phase
t 1/2 pie
Represents the equilibrium within the VRG referred to as peak half-time
Slower Distribution (Redistribution) Phase
t 1/2 alpha
Represents the distribution from the circulation (central compartment) to peripheral tissues (peripheral compartment); referred to as distribution half-time
Elimination Phase
t 1/2 beta
Time necessary for the plasma concentration of the drug to decline 50% during the elimination phase. This time is derived by measuring the time between any two points that differ by a 2-fold plasma concentration
t 1/2 beta is directly proportional to...
the Volume of distribution of the drug
t 1/2 beta is inversely proportional to...
the Clearance of the drug
Renal or hepatic disease will alter...
which effects...
-Volume of distribution and Clearance
-Effects t1/2 beta
True or False
t 1/2 beta is dependent on the dose of the drug administered
False
t 1/2 beta is independent of the dose of drug administered (1st-order kinetics only)
Elimination half-life
The time necessary to eliminate 50% of the total drug dose from the entire body (not just the plasma). Drugs can be stored in the various compartments of the body thereby decreasing plasma concentration
# of half-times vs. change in drug concentration
1-50%, 2-75%, 3-87.5%, 4-93.8%, 5-96.9%, 6-98.4%
Less than 5 1/2 times and patient not awake...
give reversal agent
Context-sensitive half-time
Time necessary for the plasma drug concentration to decrease by 50% (or any other percent) after discontinuing a continuous infusion of a specific duration (context refers to infusion duration)
Name 3 effects of Context-sensitive half-time
1. circumvents limitations of t 1/2 beta in describing post-transfusion central compartment drug pharmacokinetics
2. Effect of distribution on plasma drug concentrations varies in magnitude and direction over time and depends on the drug concentration gradients between various compartments
3. Considers the combined effects of distribution and metabolism as well as duration of continuous IV administration on drug pharmacokinetics